Bistable electric valve, in particular for a system for recovering petrol vapours in a motor vehicle

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a National Stage of International Application No. PCT/IB2015/051976 filed Mar. 18, 2015, claiming priority based on Italian Patent Application No. TO2014A000224 filed Mar. 19, 2014, the contents of all of which are incorporated herein by reference in their entirety.

The present invention relates to a bistable electric valve, in particular for a system for recovering petrol vapours in a motor vehicle.

A bistable electric valve for such an application is known for example from the United States patent application US 2004/0040547 A1. The electric valve described in this document comprises a housing body with a first union intended to be connected to the atmosphere and a second union intended to be connected to a container (canister) which collects the petrol vapours from the petrol tank of a motor vehicle. In the housing body there is defined a chamber which communicates with the aforementioned unions and in which there is provided a valve seat with which an obturator for controlling communication between said unions is associated. The obturator is integral with a permanent magnet movable between two pole shoes in the region inside a control solenoid.

Another bistable electric valve, for use in refrigerating circuits, is known from the patent application FR 2,600,150 A1.

A further bistable electric valve is described in the Italian patent IT 1,308,473 B1 in the name of the same Applicant.

An object of the present invention is to provide a bistable electric valve of the improved type, in particular for use in a system for recovering petrol vapours in a motor vehicle.

This object and other objects are achieved according to the invention by means of a bistable electric valve comprising <ul id="ul0001" list-style="none"><li id="ul0001-0001" num="0000"><ul id="ul0002" list-style="none"><li id="ul0002-0001" num="0008">a hollow housing in which there is defined a chamber having first and second openings;</li><li id="ul0002-0002" num="0009">a main obturator made of ferromagnetic material, arranged inside said chamber and displaceable between first and second working positions in which it respectively closes and opens said first opening for enabling and disabling respectively a flow of fluid from the second opening to the first opening; the main obturator having at least one calibrated through-hole for establishing communication between the region upstream and the region downstream of said obturator;</li><li id="ul0002-0003" num="0010">first and second permanent magnets, mounted in said housing in the vicinity of said first and second openings, respectively, and designed to keep the obturator in the first and second working positions, respectively;</li><li id="ul0002-0004" num="0011">an auxiliary obturator mounted movable in the region comprised between the main obturator and said second opening, upstream of the through-hole of the main obturator, between first and second positions in which it closes and opens said through-hole, respectively;</li><li id="ul0002-0005" num="0012">a third permanent magnet, integral with the auxiliary obturator; and</li><li id="ul0002-0006" num="0013">a control solenoid arranged around the path of the main obturator and the auxiliary obturator and designed to generate a magnetic flux tending to cause the attraction of the main obturator and the auxiliary obturator towards one or other of said first and second openings;</li><li id="ul0002-0007" num="0014">the arrangement being such that when the solenoid is de-energized the electric valve assumes</li><li id="ul0002-0008" num="0015">a first stable condition in which the auxiliary obturator closes the through-hole of the main obturator, and the latter is arranged in said first working position in which it closes said first opening, or</li><li id="ul0002-0009" num="0016">a second stable condition in which the main obturator is arranged in the second working condition in which it opens said first opening; and</li><li id="ul0002-0010" num="0017">when the solenoid is energized while the electric valve is in the first stable condition, the magnetic flux generated by the solenoid causes the third permanent magnet and the auxiliary obturator to pass into said second condition in which the auxiliary obturator opens the through-hole of the main obturator, and thereafter the main obturator to pass into the aforementioned second position; and</li><li id="ul0002-0011" num="0018">when the solenoid is energized while the electric valve is in the second stable condition, the magnetic flux generated by the solenoid causes the main obturator and the auxiliary obturator to return into the respective first positions.</li></ul></li></ul>

Further characteristic features and advantages of the invention will become clear from the following description provided purely by way of a non-limiting example, with reference to the accompanying drawings in which:

<figref idref="DRAWINGS">FIG. 1</figref> is a perspective view of a bistable electric valve according to the present invention;

<figref idref="DRAWINGS">FIG. 2</figref> is an axially cross-sectioned view along the line II-II of <figref idref="DRAWINGS">FIG. 1</figref>;

<figref idref="DRAWINGS">FIG. 3</figref> is a view similar to that shown in <figref idref="DRAWINGS">FIG. 2</figref> and shows another operative condition of the bistable electric valve;

<figref idref="DRAWINGS">FIG. 4</figref> is similar to the views shown in <figref idref="DRAWINGS">FIGS. 2 and 3</figref> and shows another operative condition of the bistable electric valve;

<figref idref="DRAWINGS">FIG. 5</figref> is a view similar to the preceding view and shows a further operative condition of the bistable electric valve; and

<figref idref="DRAWINGS">FIG. 6</figref> is similar to <figref idref="DRAWINGS">FIGS. 2 to 5</figref> and shows a variation of embodiment.

In the drawings <b>1</b> denotes overall a bistable electric valve according to the present invention intended in particular for use in a system for recovery of petrol vapours in a motor vehicle.

The electric valve <b>1</b> comprises a hollow support housing, denoted overall by <b>2</b>, comprising an essentially tubular central portion <b>3</b> at the ends of which respective terminal portions indicated by <b>4</b> and <b>5</b> are connected.

The portions <b>3</b> to <b>5</b> of the support housing <b>2</b> may be conveniently made of moulded plastic material, for example a polyamide 6-6.

In the example of embodiment shown the intermediate portion <b>3</b> of the support housing <b>2</b> has essentially cylindrical opposite terminal parts <b>3</b><i>a</i>, <b>3</b><i>b </i>which have substantially the same diameter, and an intermediate portion <b>3</b><i>c </i>which is also essentially cylindrical and has a smaller diameter.

The end portions <b>3</b><i>a </i>and <b>3</b><i>b </i>are connected to the intermediate portion <b>3</b><i>c </i>by means of two annular walls <b>3</b><i>d </i>and <b>3</b><i>e </i>integral therewith (see in particular <figref idref="DRAWINGS">FIGS. 2 and 3</figref>).

The terminal portions <b>4</b> and <b>5</b> of the support housing <b>2</b> have respective annular walls <b>4</b><i>a </i>and <b>5</b><i>a </i>from the central opening of which respective tubular connecting formations <b>4</b><i>b </i>and <b>5</b><i>b </i>acting as an outlet and an inlet, respectively, extend in opposite directions, said formations being axially aligned with each other along the axis A-A of the electric valve <b>1</b>.

A control winding or solenoid <b>6</b> is housed outside the support housing <b>2</b>, inside the annular cavity defined between the walls <b>3</b><i>c</i>, <b>3</b><i>d </i>and <b>3</b><i>e </i>and can be connected to a control circuit (not shown) by means of electric terminals <b>7</b> connected to its ends.

As can be more clearly seen in <figref idref="DRAWINGS">FIG. 1</figref>, a closed magnetic circuit extends around the support housing <b>2</b>, said circuit being formed with two laminations <b>8</b>, for example made of metal, folded in an L-shape and having their respective ends seamed together (see also <figref idref="DRAWINGS">FIG. 3</figref>).

A chamber <b>10</b> is defined inside the housing <b>2</b> and is able to communicate with the unions <b>4</b><i>b </i>and <b>5</b><i>b</i>, as will be described more clearly below.

The unions <b>4</b><i>a </i>and <b>5</b><i>b </i>in the embodiment shown extend through corresponding openings <b>9</b> provided in facing sections of the laminations <b>8</b> which form the external magnetic circuit (see for example <figref idref="DRAWINGS">FIGS. 1 and 2</figref>).

In <figref idref="DRAWINGS">FIGS. 2 to 5, 11 and 12</figref> denote two annular pole shoes made of ferromagnetic material, for example steel, having respective central openings <b>11</b><i>a </i>and <b>12</b><i>a </i>which are aligned with the unions <b>4</b><i>b </i>and <b>5</b><i>b</i>, respectively, of the support housing <b>2</b>.

Two annular permanent magnets <b>13</b> and <b>14</b>, for example made of FeSt, coaxial with the longitudinal axis A-A of the electric valve <b>1</b>, are positioned inside the support housing <b>2</b> between the pole shoes <b>11</b>, <b>12</b> and the annular walls <b>3</b><i>d</i>, <b>3</b><i>e. </i>

The chamber <b>10</b> defined inside the support housing <b>2</b> contains an axially displaceable main obturator made of ferromagnetic material, for example steel, denoted overall by <b>15</b> in <figref idref="DRAWINGS">FIGS. 2 to 5</figref>.

The obturator <b>15</b> in the embodiment shown comprises a first axial portion <b>15</b><i>a </i>which is essentially cup-shaped, with its inlet opening directed towards the pole shoe <b>11</b>. The edge of the inlet opening along the portion <b>15</b><i>a </i>of the obturator <b>15</b> faces a sealing O-ring <b>16</b> fixed to the surface of the pole shoe <b>11</b> which faces the obturator <b>15</b>.

The arrangement is such that when the portion <b>15</b><i>a </i>of the obturator <b>15</b> with its annular edge of the inlet opening presses against the sealing ring <b>16</b>, the chamber <b>10</b> is disconnected from the opening <b>11</b><i>a </i>of the pole shoe <b>11</b> and the union <b>4</b><i>b. </i>

The arrangement is moreover such that, when the obturator <b>15</b> is in the working position shown in <figref idref="DRAWINGS">FIGS. 2 and 3</figref> and its portion <b>15</b><i>a </i>presses against the sealing ring <b>16</b>, it is able to be retained in this position owing to the attraction exerted on it by the permanent magnet <b>13</b>, via the pole shoe <b>11</b>.

The portion <b>15</b><i>a </i>of the obturator <b>15</b> has a transverse end wall <b>15</b><i>c </i>inside which a calibrated central through-hole <b>17</b> is formed, said hole allowing communication between the upstream and downstream regions of this wall.

The main obturator <b>15</b> also has a second portion, indicated by <b>15</b><i>b</i>, in <figref idref="DRAWINGS">FIG. 2</figref> et seq. This portion is also essentially cylindrical tubular and extends on the opposite side to the portion <b>15</b><i>a </i>relative to the transverse wall <b>15</b><i>c. </i>

A plurality of longitudinal through-slits <b>15</b><i>d </i>are formed in the side wall of the portion <b>15</b><i>b </i>of the obturator, said through-slits being able to place in communication with each other the radially inner region and the radially outer region of said portion of the obturator <b>15</b>.

A support ring <b>18</b>, for example made of moulded plastic, such as a polyamide 6-6, is firmly connected to the annular end edge of the portion <b>15</b><i>b </i>of the main obturator <b>15</b>.

This ring <b>18</b> axially faces a sealing O-ring <b>19</b> fixed to the pole shoe <b>12</b>.

Inside the annular member <b>18</b> there extends an essentially cup-shaped body <b>20</b> arranged so that its inlet opening is directed towards the intermediate transverse wall <b>15</b><i>c </i>of the main obturator <b>15</b>. This body <b>20</b> is connected to the support element <b>18</b> by means of a plurality of spokes <b>18</b><i>a </i>between which a plurality of axial passages <b>18</b><i>b </i>are defined.

The ring <b>18</b>, the body <b>20</b> and the spokes <b>18</b><i>a </i>may be conveniently formed as one piece.

The passages <b>18</b><i>b </i>face the opening <b>12</b><i>a </i>of the pole shoe <b>12</b>.

As will emerge more clearly below, the main obturator <b>15</b> is able to assume a second working position, shown in <figref idref="DRAWINGS">FIG. 4</figref>, where the support ring <b>18</b>, integral therewith, presses against the sealing O-ring <b>19</b>.

In the condition shown in <figref idref="DRAWINGS">FIG. 4</figref>, the chamber <b>10</b> moreover communicates with the region inside the union <b>4</b><i>b </i>and the opening <b>11</b><i>a </i>of the pole shoe <b>11</b>, since the portion <b>15</b><i>a </i>of the obturator <b>15</b> is spaced from the sealing O-ring <b>16</b>. Therefore, in the condition shown in <figref idref="DRAWINGS">FIG. 4</figref>, the electric valve <b>1</b> is completely pervious between the unions <b>4</b><i>b </i>and <b>5</b><i>b. </i>

A permanent magnet <b>21</b> is mounted axially displaceable inside the body <b>20</b>. This permanent magnet, on the side directed towards the intermediate transverse wall <b>15</b><i>c </i>of the main obturator <b>15</b> has an auxiliary obturator <b>22</b> operationally cooperating with the calibrated hole <b>17</b> in order to form a so-called pilot valve.

A spring <b>23</b> may be arranged between the permanent magnet <b>21</b> and the end wall <b>20</b><i>a </i>of the body <b>20</b>, said spring tending to push this permanent magnet and the associated obturator <b>22</b> towards the intermediate transverse wall <b>15</b><i>c </i>of the obturator <b>15</b> and the calibrated through-hole <b>17</b> of the latter.

The main obturator <b>15</b>, as already mentioned above, is able to assume a first and a second stable working position.

In the first position, shown for example in <figref idref="DRAWINGS">FIGS. 2 and 3</figref>, the portion <b>15</b><i>a </i>of this obturator <b>15</b> presses against the sealing ring <b>16</b> and disconnects the chamber <b>10</b> and the inner region of the union <b>5</b><i>b </i>from the union <b>4</b><i>b</i>. The obturator <b>15</b><i>a </i>is retained in this position owing to the attraction exerted on it by the permanent magnet <b>13</b>.

In the second stable working position, shown in <figref idref="DRAWINGS">FIG. 4</figref>, the main obturator <b>15</b> enables communication between the chamber <b>10</b>, the opening <b>11</b><i>a </i>and the union <b>4</b><i>b</i>, in fact establishing communication between the unions <b>4</b><i>b </i>and <b>5</b><i>b</i>. The main obturator <b>15</b> is able to be kept in the position shown in <figref idref="DRAWINGS">FIG. 4</figref> by the effect of the attraction exerted on it by the permanent magnet <b>14</b>.

During use, the inlet union <b>5</b><i>b </i>of the electric valve <b>1</b> is intended to be connected to a fluid source under a certain pressure, for example a canister containing petrol vapours. This fluid, when the electric valve is closed, fills the chamber <b>16</b>.

An operating cycle of the aforementioned electric valve <b>1</b> will now be described, starting from the operative condition shown in <figref idref="DRAWINGS">FIG. 2</figref>.

In the condition shown in <figref idref="DRAWINGS">FIG. 2</figref>, the solenoid <b>6</b> is de-energized and the main obturator <b>15</b> is in the first working position described above, namely pressed against the sealing O-ring <b>16</b>, disconnecting the chamber <b>10</b> from the opening <b>11</b><i>a </i>and the union <b>4</b><i>b. </i>

In this condition the auxiliary obturator closes off the calibrated hole <b>17</b> of the intermediate transverse wall <b>15</b><i>c </i>of the main obturator <b>15</b>. The electric valve <b>1</b> overall therefore is closed.

If, while the electric valve <b>1</b> is in the condition shown in <figref idref="DRAWINGS">FIG. 2</figref>, the control winding or solenoid <b>6</b> is energized, by means of a current flow circulating in a first predetermined direction, the magnetic field generated by this winding or solenoid causes firstly a displacement of the permanent magnet <b>21</b> and the associated auxiliary obturator <b>22</b> away from the intermediate transverse wall <b>15</b><i>c </i>of the main obturator <b>15</b>, as shown in <figref idref="DRAWINGS">FIG. 3</figref>.

A first condition is thus assumed where the chamber <b>10</b> is placed in communication with the opening <b>11</b><i>a </i>and the union <b>4</b><i>b </i>via the small calibrated hole <b>17</b>.

The pressurized fluid contained in the chamber <b>10</b> may therefore gradually spread through the hole <b>17</b>, beyond the wall <b>15</b><i>c </i>of the main obturator. As a result the pressure which this fluid inside the chamber <b>10</b> exerts against the main obturator <b>15</b> gradually diminishes in the direction of the sealing O-ring <b>16</b>.

At a certain point, since this pressure is no longer present, the magnetic field produced by the winding or solenoid <b>6</b> is stronger than the attraction which the permanent magnet <b>13</b> exerts on the main obturator <b>15</b>, and the latter therefore abandons the first working position and moves towards the second working position shown in <figref idref="DRAWINGS">FIG. 4</figref>.

As a result of this displacement, the chamber <b>10</b> is placed in communication with the opening <b>11</b><i>a </i>and the union <b>4</b><i>b </i>via a very broad section such that the unions <b>5</b><i>b </i>and <b>4</b><i>b </i>fully communicate. The winding or solenoid <b>6</b> may therefore be de-energized, but the main obturator <b>15</b> remains in the second working position, shown in <figref idref="DRAWINGS">FIG. 4</figref>, owing to the attraction exerted on it now by the permanent magnet <b>14</b>.

This condition is again a stable condition in which the electric valve <b>1</b> does not use energy since the winding or solenoid <b>6</b> is de-energized.

In this condition, owing to the mutual attraction between the magnet <b>21</b> and the main obturator <b>15</b> as well as the thrust of the spring <b>23</b>, where present, the auxiliary obturator <b>22</b> closes off the calibrated passage <b>17</b>. This, however, does not prevent full communication between the unions <b>5</b><i>b </i>and <b>4</b><i>b </i>through the passages <b>18</b><i>b </i>defined in the annular support member <b>18</b>, the eyelets <b>15</b><i>d </i>of the main obturator <b>15</b> and the opening <b>11</b><i>a </i>formed in the pole shoe <b>11</b>.

When the winding or solenoid <b>6</b> is again energized while the solenoid valve <b>1</b> is in the stable condition shown in <figref idref="DRAWINGS">FIG. 4</figref>, this time, by means of a current flow circulating in a second direction, opposite to the preceding direction, the magnetic field generated by the solenoid causes both the permanent magnet <b>21</b> and the main obturator <b>15</b> to pass from the condition shown in <figref idref="DRAWINGS">FIG. 4</figref> to the condition shown in <figref idref="DRAWINGS">FIG. 2</figref>.

The electric valve <b>1</b> is then closed again.

After the winding or solenoid <b>6</b> has been de-energized again, the electric valve <b>1</b> remains in the stable condition shown in <figref idref="DRAWINGS">FIG. 2</figref> as a result of the attraction between the permanent magnet <b>13</b> and the main obturator <b>15</b> and between the latter and the permanent magnet <b>21</b>.

If, while the electric valve <b>1</b> is located in the stable condition shown in <figref idref="DRAWINGS">FIG. 2</figref>, a counter-pressure is formed in the outlet union <b>4</b><i>b </i>and in the opening <b>11</b><i>a </i>as well as inside the portion <b>15</b><i>a </i>of the main obturator <b>15</b>, this counter-pressure causes the assembly formed by the auxiliary obturator <b>22</b> and by the associated permanent magnet <b>21</b> to move away from the calibrated hole <b>17</b>.

This counter-pressure may then be vented inside the chamber <b>10</b>, through the momentarily open hole <b>17</b>.

Once the counter-pressure has been released, the obturator <b>22</b> and the magnet <b>21</b> assume again the condition shown in <figref idref="DRAWINGS">FIG. 2</figref>.

<figref idref="DRAWINGS">FIG. 6</figref> shows a variation of embodiment.

In this figure parts and elements already described have again been assigned the same reference numbers and letters used previously.

The variant according to <figref idref="DRAWINGS">FIG. 6</figref> differs from the embodiment described previously essentially because the two groups formed by the pole shoes <b>11</b> and <b>12</b> and by the associated permanent magnets <b>13</b> and <b>14</b> are wholly replaced by corresponding annular permanent magnets indicated by <b>31</b> and <b>32</b> in <figref idref="DRAWINGS">FIG. 6</figref>. These magnets <b>31</b> and <b>32</b> may be made of plastoferrite or plasto-neodymium.

The operating modes of the variation of embodiment according to <figref idref="DRAWINGS">FIG. 6</figref> are practically identical to those of the embodiment described and illustrated with reference to the preceding figures and will therefore not be further described.

Obviously, without altering the principle of the invention, the embodiments and the constructional details may be greatly varied with respect to that described and illustrated purely by way of a non-limiting example, without thereby departing from the scope of the invention as defined in the accompanying claims.